Soldering connector pins to the plated-through holes of circuits boards is a labor intensive and tedious operation with many pitfalls. Too much solder may result in a short between two adjacent pins. Too little solder may result in an inadequate electrical connection between the pin and the plated-through hole. The right amount of solder wrongly placed results in too much solder on the surface of the circuit board and too little solder in the plated-through hole to make a connection that will withstand vibration.
Thus, the art has long sought a simple method that will ensure that the correct amount of solder is placed in the proper position around each pin and at each plated-through hole.
The invention overcomes the above-noted and other drawbacks of the prior art by providing a method for applying solder preforms to contacts of connectors which features a capability of depositing the exact amount of solder required in the exact position required. This invention eliminates that undesirable feature common to existing methods wherein the solder is sequentially applied to each individual contact of a connector. The invention is the first successful method of applying solder to connector contacts which simultaneously applies the desired amount of solder preforms in the correct position to all the contacts of a given connector.
In the method of the present invention, a water-soluble adhesive material is perforated to form perforations in a pattern according to the arrangement of the pins of a connector, solder preforms are applied around the perforations, the pins of the connector are inserted through the holes of a circuit board; and then the adhesive material is positioned against the circuit board to center the solder preforms around the pins. The adhesive material is then washed off, e.g., with water. Finally, the pins of the connector are heated to the flow-point temperature of the solder.